(1) Technical Field
The present invention relates to a solid-state imaging device including a multilayer wiring layer, color filters, and lenses, and a manufacturing method for the same, and in particular to a technology for appropriately adjusting the thicknesses of color filters and lenses so as to suppress unevenness in the thicknesses thereof between pixels.
(2) Background Art
A solid-state imaging device, such as a CMOS image sensor and a CCD image sensor, is provided with a pixel region, in which a plurality of pixels are arranged in a matrix. In each of the pixels within the pixel region, a light receiver which outputs imaging signals in accordance with the amount of light incident thereto and an area corresponding to the light receiver which transmits imaging signals are disposed in one main surface of a semiconductor substrate. In addition, such a solid-state imaging device also includes a peripheral circuit region similarly provided on the main surface of the semiconductor substrate and which performs drive control of the pixel region and signal processing of the imaging signals.
There have been various proposals made throughout the years of technologies for enhancing the optical characteristics of such a solid-state imaging device. One example of such technology is the waveguide technology, which allows photodiodes in the solid-state imaging device to receive incident light with increased efficiency.
A waveguide consists of a core (a portion of a waveguide member) which functions as an optical path for incident light, and a cladding (an interlayer insulating film) which surrounds the core. By selecting an appropriate material for each of the core and the cladding, incident light entering the waveguide via the color filter and the lens is reflected at a boundary surface between the core and the cladding, and is received by the photodiode with only a minimal amount of light being lost.
However, concerning such solid-state imaging devices having the waveguide formed therein, there lies a problem in that a difference in terms of level, with respect to the main surface of a substrate on which the solid-state imaging device is formed, exists between the top surface of the pixel region and the top surface of the peripheral circuit region. Such difference in level results in an incline being formed on areas of the color filter film and the lens film when the color filter film and the lens film are successively disposed onto the top surfaces of the pixel region and the peripheral circuit region having the waveguide member disposed thereon. The forming of such an incline is problematic in that differences arise in the thicknesses and the shapes of the color filter film and the lens film within the pixel region. If the films have ununiform thicknesses and shapes within the pixel area, an ununiform amount of light is produced by pixels of the yielded solid-state imaging device. Furthermore, such unevenness in thicknesses and shapes of the films may lead to pixels of the solid-state imaging device having ununiform sensitivity levels, which further results in unevenness in terms of color and sensitivity.
Since such unevenness in color and sensitivity is caused by the unevenness in the amount of light produced by pixels as mentioned above, the same problems occur not only in solid-state imaging devices to which the waveguide technology has been applied, but in all conventional solid-state imaging devices.
With such problems in consideration, Patent Literature 1 discloses a structure for reducing the aforementioned level difference formed between the pixel region and the peripheral circuit region. In detail, Patent Literature 1 suggests reducing the aforementioned incline formed in a conventional solid-state imaging device by disposing a groove (a concave) in an insulating film disposed on the multilayer wiring layer within the pixel region, and applying a color filter material on the insulating film having the groove provided therein.